The present invention relates to an apparatus and to a method of sterilizing inner walls of containers with at least one electron beam emitter.
Apparatus for the sterilization of containers are incorporated for example in production and filling plants of container and bottle manufacturers, in order preferably to permit a sterilization of the interior space of the containers which is brought into contact with the medium to be received in the container.
A sterilization of the containers can be carried out in this case by means of different methods. In this way for example, a liquid or flowable sterilization agent (chemical sterilization) can be applied to the inner wall of the container or the container can be immersed in an agent of this type, in which case, however, the container usually still has to be rinsed and dried after the sterilization in order to prevent a negative interaction between the sterilization agent and the filled medium.
Steam or hot air sterilization, i.e. the sterilization by heating, is likewise known, in which case, however, the containers to be sterilized have to be heated to extremely high temperatures in order to permit a substantially complete sterilization of the containers by destruction of the bacteria. This could also lead to the deformation of and long-term damage to the containers to be sterilized, so that a method of this type cannot be used, in particular in the region of the production of plastics material containers.
Sterilization by means of radiation is also a method which is preferably used in the case of containers already expanded into their final shape, in order to achieve a complete sterilization in this way. Electron beams which are emitted by an electron beam emitter and which are introduced into the interior space of the container are preferably used as the radiation in this case.
In this way for example, DE 10 2008 045 187 A1 also discloses a method of sterilizing containers, in which a treatment head is introduced into the interior of the blow-moulded bottle, emits radiation and applies it to the internal surface of the bottle. This treatment head or radiation finger is designed in its construction in such a way that it is possible to sterilize containers such as bottles etc. which are already expanded into their final size and shape and which, in addition, have at least one defined bottle aperture diameter and a defined wall diameter in order to allow the treatment head or the distal end thereof to penetrate into the interior of the container and to irradiate the internal surface over the complete periphery for sterilization purposes.
On account of their function, however, treatment heads of this type have a minimum external diameter of approximately 16 mm and, in this way, although they can be inserted through the majority of container apertures, they cannot be inserted into conventional pre-forms since the internal diameter of these pre-forms is reduced with respect to the distal end, as viewed from the aperture.
This means that, if—instead of sterilizing or irradiating already completely shaped-out containers or bottles—pre-forms are preferably to be irradiated and thus sterilized, when a treatment head of this type is used and introduced into the aperture area of the pre-form just behind the aperture thereof a very large radiation dosage would strike the surface of the interior space of the container, whereas in contrast an excessively small radiation dosage would be applied to the internal surface of the distal end, i.e. the lower closed end, of the pre-form, as a result of which a reliable sterilization over the entire periphery of the inner wall of the pre-form would no longer take place.
Accordingly, the object of the present invention is to make available an apparatus and a method of sterilizing inner walls of containers and, in particular, of pre-forms, which shadows areas of the container not to be sterilized, and the radiation striking the aperture area in an over-metered manner is transmitted to the lower distal areas of the container in such a way that it is consequently possible to ensure a substantially uniform irradiation of the entire interior space of the container.